{"id":"CVE-2026-99093","state":"PUBLISHED","title":"mm: don't schedule deferred kernel page table freeing while booting","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nmm: don't schedule deferred kernel page table freeing while booting\n\nBooting with a boot-time function tracer and a filter, for example\n\n  ftrace=function ftrace_filter=pud_free_pmd_page\n\npanics on 7.3-rc4 as soon as the tracer starts:\n\n  [   23.531178] Starting tracer 'function'\n  [   23.675800] Oops: general protection fault, probably for non-canonical address 0xdffffc0000000038: 0000 [#1] SMP KASAN NOPTI\n  [   23.819917] KASAN: null-ptr-deref in range [0x00000000000001c0-0x00000000000001c7]\n  [   23.964025] CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 7.3.0-rc4-fe2ec83746e5-with-fixes-v2+ #195 PREEMPT(undef)\n  [   24.252248] RIP: 0010:__queue_work+0xab/0xf00\n  [   25.981629] Call Trace:\n  [   26.125727]  <TASK>\n  [   26.413912]  ? pagetable_free_kernel+0x20/0x120\n  [   26.990283]  queue_work_on+0x97/0xf0\n  [   27.134382]  __cpa_collapse_large_pages+0x501/0x6f0\n  [   27.566662]  cpa_flush+0x394/0x620\n  [   27.998953]  change_page_attr_set_clr+0x321/0x4a0\n  [   29.151729]  set_memory_rox+0xa2/0xf0\n  [   29.584018]  create_trampoline+0x431/0x6f0\n  ...\n  [   44.343347] Kernel panic - not syncing: Attempted to kill the idle task!\n\nThe boot-time tracer is started from early_trace_init(), which runs\nbefore workqueue_init_early().  Making its trampoline read-only splits a\nlarge page, and CPA collapses it again right away.  The split table has\nbeen a kernel page table since commit 9e4a3ec3411b\n(\"x86/mm/pat: Allocate split page tables as kernel page tables\"), so the\ncollapse frees it through pagetable_free_kernel(), which queues work on\nsystem_percpu_wq - still NULL at that point.  That commit is correct in\nitself; it only lets CPA reach pagetable_free_kernel() before the\nworkqueue that function relies on exists.\n\nKeep putting the table on the list, but don't schedule the work while\nthe system is still booting.  A core_initcall schedules it once to free\nwhatever was queued by then.","publishedAt":"2026-10-26T14:52:01.450Z","updatedAt":"2026-10-26T14:52:01.450Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"84e0cd79d57f06b872154eb5d8f610584133f260","status":"affected","lessThan":"7a25ca170c12a9328f6fcf4410713beb516b01c0","versionType":"git"},{"version":"922873cf4fc34124215070a8ad391bf831538bb9","status":"affected","lessThan":"df6c704a08bc0925d5db047b0a6221f962bda4d9","versionType":"git"},{"version":"9e4a3ec3411bb6bb59e3c1f29b75609f1e87aac4","status":"affected","lessThan":"2fb552b0bee70c24c092720028ab4620f5eb2646","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["mm/pgtable-generic.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"6.18.53","status":"affected","lessThan":"6.18.57","versionType":"semver"},{"version":"7.2.7","status":"affected","lessThan":"7.2.11","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["mm/pgtable-generic.c"]}],"references":["https://git.kernel.org/stable/c/7a25ca170c12a9328f6fcf4410713beb516b01c0","https://git.kernel.org/stable/c/df6c704a08bc0925d5db047b0a6221f962bda4d9","https://git.kernel.org/stable/c/2fb552b0bee70c24c092720028ab4620f5eb2646"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:43.249Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/99xxx/CVE-2026-99093.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-99093","state":"PUBLISHED","datePublished":"2026-10-26T14:52:01.450Z","dateUpdated":"2026-10-26T14:52:01.450Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-25T10:25:14.390Z"},"containers":{"cna":{"title":"mm: don't schedule deferred kernel page table freeing while booting","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nmm: don't schedule deferred kernel page table freeing while booting\n\nBooting with a boot-time function tracer and a filter, for example\n\n  ftrace=function ftrace_filter=pud_free_pmd_page\n\npanics on 7.3-rc4 as soon as the tracer starts:\n\n  [   23.531178] Starting tracer 'function'\n  [   23.675800] Oops: general protection fault, probably for non-canonical address 0xdffffc0000000038: 0000 [#1] SMP KASAN NOPTI\n  [   23.819917] KASAN: null-ptr-deref in range [0x00000000000001c0-0x00000000000001c7]\n  [   23.964025] CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 7.3.0-rc4-fe2ec83746e5-with-fixes-v2+ #195 PREEMPT(undef)\n  [   24.252248] RIP: 0010:__queue_work+0xab/0xf00\n  [   25.981629] Call Trace:\n  [   26.125727]  <TASK>\n  [   26.413912]  ? pagetable_free_kernel+0x20/0x120\n  [   26.990283]  queue_work_on+0x97/0xf0\n  [   27.134382]  __cpa_collapse_large_pages+0x501/0x6f0\n  [   27.566662]  cpa_flush+0x394/0x620\n  [   27.998953]  change_page_attr_set_clr+0x321/0x4a0\n  [   29.151729]  set_memory_rox+0xa2/0xf0\n  [   29.584018]  create_trampoline+0x431/0x6f0\n  ...\n  [   44.343347] Kernel panic - not syncing: Attempted to kill the idle task!\n\nThe boot-time tracer is started from early_trace_init(), which runs\nbefore workqueue_init_early().  Making its trampoline read-only splits a\nlarge page, and CPA collapses it again right away.  The split table has\nbeen a kernel page table since commit 9e4a3ec3411b\n(\"x86/mm/pat: Allocate split page tables as kernel page tables\"), so the\ncollapse frees it through pagetable_free_kernel(), which queues work on\nsystem_percpu_wq - still NULL at that point.  That commit is correct in\nitself; it only lets CPA reach pagetable_free_kernel() before the\nworkqueue that function relies on exists.\n\nKeep putting the table on the list, but don't schedule the work while\nthe system is still booting.  A core_initcall schedules it once to free\nwhatever was queued by then."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"84e0cd79d57f06b872154eb5d8f610584133f260","status":"affected","lessThan":"7a25ca170c12a9328f6fcf4410713beb516b01c0","versionType":"git"},{"version":"922873cf4fc34124215070a8ad391bf831538bb9","status":"affected","lessThan":"df6c704a08bc0925d5db047b0a6221f962bda4d9","versionType":"git"},{"version":"9e4a3ec3411bb6bb59e3c1f29b75609f1e87aac4","status":"affected","lessThan":"2fb552b0bee70c24c092720028ab4620f5eb2646","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["mm/pgtable-generic.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"6.18.53","status":"affected","lessThan":"6.18.57","versionType":"semver"},{"version":"7.2.7","status":"affected","lessThan":"7.2.11","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["mm/pgtable-generic.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/7a25ca170c12a9328f6fcf4410713beb516b01c0"},{"url":"https://git.kernel.org/stable/c/df6c704a08bc0925d5db047b0a6221f962bda4d9"},{"url":"https://git.kernel.org/stable/c/2fb552b0bee70c24c092720028ab4620f5eb2646"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-26T14:52:01.450Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.18.53","versionEndExcluding":"6.18.57"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"7.2.7","versionEndExcluding":"7.2.11"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}